This invention relates to an inkjet ink composition comprising a dye and a hyperbranched polymer.
Ink jet printing is a non-impact method for producing images by the deposition of ink droplets in a pixel-by-pixel manner to an image-recording element in response to digital signals. There are various methods which may be utilized to control the deposition of ink droplets on the image-recording element to yield the desired image. In one process, known as continuous ink jet, a continuous stream of droplets is charged and deflected in an imagewise manner onto the surface of the image-recording element, while unimaged droplets are caught and returned to an ink sump. In another process, known as drop-on-demand ink jet, individual ink droplets are projected as needed onto the image-recording element to form the desired image. Common methods of controlling the projection of ink droplets in drop-on-demand printing include piezoelectric transducers and thermal bubble formation. Inkjet printers have found broad applications across markets ranging from industrial labeling to short run printing to desktop document and pictorial imaging.
The inks used in the various ink jet printers can be classified as either dye-based or pigment-based. A dye is a colorant which is dissolved or dispersed in the carrier medium. A pigment is a colorant that is insoluble in the carrier medium, but is dispersed or suspended in the form of small particles, often stabilized against flocculation and settling by the use of dispersing agents. The carrier medium can be a liquid or a solid at room temperature in both cases. Commonly used carrier media include water, mixtures of water and organic co-solvents and high boiling organic solvents, such as hydrocarbons, esters, ketones, etc.
In traditional dye-based inks, no particles are observable under the microscope. Although there have been many recent advances in the art of dye-based ink jet inks, such inks still suffer from deficiencies such as low optical densities on plain paper and poor light-fastness. When water is used as the carrier, such inks also generally suffer from poor water fastness and poor smear resistance. These problems can be minimized by replacing the dyes used in ink formulations with insoluble pigments. In general, pigments are superior to dyes with respect to waterfastness, lightfastness, and stability towards pollutants in the air. However, the pigment inks tend to be unstable and settle out from the liquid vehicle over a long storage time. Pigment inks also have a tendency to clog the orifices of the printhead resulting in deterioration of print quality.
Accordingly, there is a need for inks having advantages of both dye-based inks and pigment based inks that have good lightfastness, stability towards pollutants, waterfastness and reliability in the printhead.
U.S. patent application Ser. No. 09/742,961, filed Dec. 20, 2000, discloses an inkjet printing method using an ink jet ink comprising a water soluble dye and a water dispersible polymer latex. However, there is a problem with this ink composition in that its viscosity is high, resulting in poor firability from a thermal ink jet printhead.
WO 00/37542 discloses a pigment-based ink jet ink using dendritic polymers as a dispersant. However, there is a problem with this ink in that the ink tends to be unstable and settles out from the liquid vehicle over a long storage time, and has a tendency to clog the orifices of the printhead.
Wang et. al. in pending U.S. patent application Ser. No. 09/918,584 filed Jul. 30, 2001 describes an ink jet ink composition comprising a hyperbranched polymeric dye to give improved dye stability and firability. However, there is still a need to improve the stability and firability without having to link the dye covalently through polymer synthesis.
It is an object of this invention to provide an inkjet ink composition that, when printed, provides an image which has improved waterfastness, lightfastness, and stability towards pollutants such as ozone. It is another object of this invention to provide an ink jet ink composition that has improved firability through an ink jet printhead.
These and other objects are achieved in accordance with this invention which relates to an inkjet ink composition comprising water, a humectant, a dye, and a hyperbranched polymer.
It has been found that this ink jet ink composition, when printed, provides an image which has improved waterfastness, lightfastness, and stability towards pollutants such as ozone and has improved firability through an ink jet printhead.
Any hyperbranched polymer that is soluble or dispersible in an ink jet ink may be used in the invention. A dispersible hyperbranched polymer is one that can form a colloid in an inkjet ink with a particle size being less than 10 xcexcm, preferably less than 500 nm, more preferably less than 200 nm.
Any hyperbranched polymer with various topologies and compositions may be used in the invention, e.g., homo-hyperbranched, random hyperbranched, block hyperbranched, graft hyperbranched, star hyperbranched, etc.
A hyperbranched polymer is defined as a polymer formed by polymerization of one or more branching monomers with or without no-branching monomers as described in J. Am. Chem. Soc., 74, p2718 (1952), the disclosure of which is hereby incorporated by reference. The terms xe2x80x9chyperbranchedxe2x80x9d used herein with respect to branched polymers are intended to designate polymers having a relatively high percentage of propagated branching sites per number of polymerized monomer units, e.g., at least one branching site per every ten monomer units, preferably at least one branching site per every five monomer units, and more preferably, at least one branching site per every two monomer units.
In general, hyperbranched polymers used in the present invention can be made through a chain polymerization or condensation polymerization processes, as described in J. Polym. Sci., Part A: Polym. Chem. 36, 1685-1698 (1998) and U.S. Pat. No. 4,857,630, the disclosures of which are hereby incorporated by reference. Specifically, the hyperbranched polymer used in the present invention can be made through the polymerization of An-R1-Bm monomers, wherein n and m are integers of at least 1 and R1 represents a linking group between A and B or co-polymerization of As+Bt co-monomer pairs wherein s and t are integers of at least 2 and of at least 3, respectively, as described in U.S. Pat. No. 4,857,630, and co-pending Wang et al U.S. patent applications Ser. Nos. 09/697,205; 09/919,096; 09/919,390; and 09/919,097, filed Jul. 30, 2001, the disclosures of each of which are hereby incorporated by reference.
In a preferred embodiment, the hyperbranched polymer used in the invention is a polyamnide, polyester, polyether, vinylic polymer, polyimine, polysiloxane, polyurethane, polythioether, polyarylalkylene, polysilane, or polyesteramide.
In another preferred embodiment of the invention, the hyperbranched polymer is prepared by a chain polymerization of a monomer of the formula M1n-R1-M2m wherein (i) R1 is a substituted or non-substituted straight, cyclic or branched alkyl, alkenyl, or aryl moiety and hetero atom containing substituted or non-substituted straight, cyclic or branched alkyl, alkenyl, or aryl moiety; (ii), M1 and M2 are reactive groups that react independently of each other in which M1 is a polymerization group and M2 is a precursor of a moiety M2* which initiates the polymerization of M1 as a result of being activated by any source; and (iii), n and m are integers of at least 1, more preferably n is 1 and m is 1 or 2, most preferably n is 1 and m is 1.
In another preferred embodiment of the invention, the hyperbranched polymer is prepared by a condensation or addition polymerization of a monomer of the formula M3g-R1-M4t wherein (i) R1 is defined above; (ii), M3 and M4 are groups that undergo a condensation or addition reaction with or without a catalyst; and (iii), s is an integer of at least 1 and t at least 2, more preferably s is 1 and t is 2 to 4, and most preferably s is 1 and t is 2.
In another preferred embodiment of the invention, hyperbranched polymer is prepared by a condensation or addition polymerization of a comonomer pair of the formula R2-M5x and R3-M6y wherein (i) R2 and R3 are each dependently substituted or non-substituted straight, cyclic or branched alkyl, alkenyl, or aryl moiety or hetero atom containing substituted or non-substituted straight, cyclic or branched alkyl, alkenyl, or aryl moiety; (ii), M5 and M6 are groups that undergo a condensation or addition reaction; and (iii), x is an integer of at least 2 and y an integer of at least 3, more preferably x is 2 and 4 and y is 3 to 10, and most preferably x is 2 and y is 3.
In another preferred embodiment of the invention,
M1 is a non-substituted or substituted vinylic group or epoxy; and
M2 is X, xe2x80x94CH2X, xe2x80x94CH(CH3)X, xe2x80x94C(O)CH2X, xe2x80x94C(O)CHX2, xe2x80x94C(O)CX3,
xe2x80x94OC(O)CH2X, xe2x80x94OC(O)CHX2, or xe2x80x94OC(O)CX3 wherein:
X is Cl , Br, I, Sxe2x80x94C(xe2x95x90S)xe2x80x94NR4R5, Sxe2x80x94C(xe2x95x90S)xe2x80x94OR4, xe2x80x94Oxe2x80x94NR4R5, OH or 
xe2x80x83wherein R4 and R5 are each independently xe2x80x94(CH2)r, xe2x80x94C6H5, xe2x80x94C(O)O or xe2x80x94C(O);
R7, R8 and R9 are each independently a linear or branched alkyl or aromatic group; and
rxe2x95x901-12.
In another preferred embodiment of the invention, M3 and M4 are each independently xe2x80x94COOH, xe2x80x94OH, xe2x80x94C(O)Cl, 
anhydride, NH, or NH2.
In another preferred embodiment of the invention,
M5 and M6 are each independently xe2x80x94COOH, xe2x80x94OH, xe2x80x94C(O)Cl, epoxy,
xe2x80x83anhydride, xe2x80x94NH, xe2x80x94NH2 or 
R2 is xe2x80x94C6H3xe2x80x94 or xe2x80x94(CH2)qxe2x80x94C(R6)xe2x80x94,
wherein R6 is a linear or branched alkyl or aromatic group and q is 1-6; and
R3 is xe2x80x94C6H4xe2x80x94, xe2x80x94C6H4xe2x80x94Oxe2x80x94C6H4xe2x80x94, xe2x80x94C6H3, xe2x80x94N(CH2)3, xe2x80x94C4H8xe2x80x94, xe2x80x94C6H10xe2x80x94, 
In still another embodiment of the invention, R1, R2, and R3 are each independently an oligomeric or polymeric chain of a polyamide, polyester, polyether, vinylic polymer, polyimine, polysiloxane, polyurethane, polythioether, polyarylalkylene, polysilane, or polyesteramide.
Examples of M1-R1-M2m include: 
wherein h is an integer of at least 1;
W is xe2x80x94C(O)CH2X, xe2x80x94C(O)CHX2 or xe2x80x94C(O)CX3; and
X is Cl, Br, I, 
NR4R5 or O-NR4R5, where R4 and R5 are defined as above, and R7, R8 and R9 are each independently a linear or branched alkyl or aromatic group.
Examples of M3s-R2-M4t include 2,2-bis(hydroxymethyl)propionic acid, 2,3-diaminoproponic acid, 2,5-diaminopentanoic acid, 1-Lysine and other ones having the following structure: 
wherein R10 and R11 are independently H, substituted or non-substituted straight or branched alkyl, alkenyl, aryl moiety and may be joined to form an alkylene group, 3 to 8-membered ring, h is defined above.
Examples of R2-M5x and R3-M6y include JEFFAMINE(copyright), diaminohexane, 3,3xe2x80x2-diamino-N-methylpropylamine, 1,4-phenylenediamine, 4,4xe2x80x2-oxydianiline, succinic acid, adipic acid, 1,4-cyclohexanedicarboxilic acid, terephthalic acid, 4,4xe2x80x2-oxybis(benzoic acid), 2-aminoterephtalic acid, tris(2-aminoethyl)amine, trimesic acid, maleic anhydride, succinic anhydride, hexahydrophthalic anhydride, phthalic anhydride, glutaric anhydride, octenyl anhydride, decanyl anhydride, 2-dodecenyl-1-yl-succinic anhydride, octen-1-ylsuccinic anhydride, 1,2,3,4-cyclopentane-tetra-carboxylic dianhydride, diethanolamine, diisopropanolamine, 1,2,7,8-diepoxyoctane, 1,1,1-tris(hydroxylmethyl)ethane, triethanolamine, diglycidyl-1,2-cyclohexanedicaboxylate, diglycidyl-1,2,3,6-tetrahydrophtalate, poly(propyleneglycol) diglycidyl ether, poly(dimethylsioxane) diglycidyl ether, bisphenol A propoxylate (lPO/phenol) diglycidyl ether, bis(4-glycidyloxyphenyl)methane, resorcinol diglycidyl ether, diglycidyl aniline, triphenylolmethane tridiglycidyl ether, trimethylolpropane tridiglycidyl ether, N,N-diglycidyl-4-glycidyloxybenzene, tris-2(2,3-epoxypropyl)isocyanurate, terephthaloyl chloride, 1,3,5-benzenetricarbonyl trichloride, aminopropyl terminated polydimethylsiloxanes with molecular weight from 800 to 300,000, and aminopropyl methylsiloxane-dimethylsiloxane copolymers with molecular weight from 4,000 to 5,000 and molar percentage of aminopropyl methylsiloxane from 2 to 7.
In a preferred embodiment of the invention, the soluble or dispersible hyperbranched polymer possesses water soluble or dispersible segment groups either at the ends thereof or in the backbone. These water soluble or dispersible segments or groups can be introduced by either direct polymerization or by post-modification of the hyperbranched polymer.
In another preferred embodiment of the invention, the water soluble or water dispersible segment or groups are cationic, anionic, and non-charged.
In another preferred embodiment of the invention, the anionic segments or groups are carboxylic acids and their salts, sulfonic acid and their salts, or phosphonic acid and their salts.
In another preferred embodiment of the invention, the cationic segments or groups are N and P containing quaternized onium salts.
In another preferred embodiment of the invention, the non-charged segments or groups arexe2x80x94OH, polyether, substituted or non-substitute amines.
The dyes used in this invention can be either water-soluble or water insoluble. Examples of a water soluble dye includes a reactive dye, direct dye, anionic dye, acid dye, basic dye, mono- or poly-azo dye, phthalocyanine dye, methine or polymethine dye, merocyanine dye, azamethine dye, azine dye, quinophthalone dye, thiazine dye, oxazine dye, anthraquinone or a metal-complex dye, or dyes as disclosed in U.S. Pat. No. 5,973,026, the disclosure of which is hereby incorporated by reference. In a preferred embodiment of the invention the water-soluble dye may be a cationic or an anionic dye.
In a preferred embodiment of the invention, cationic dyes are used such as azo dyes, e.g., quaternized pyrazoleazoaniline dyes as disclosed in U.S. patent application Ser. No. 09/643,281, filed Aug. 22, 2000; triarylmethine dyes; azine dyes; phthalocyanine dyes; oxazine dyes or thiazine dyes.
In another preferred embodiment of the invention, anionic dyes which may be used include a mono or poly azo dye, such as a pyrazoleazoindole dye as disclosed in U.S. patent application Ser. No. 09/689,184 filed Oct. 12, 2000; a metal-complex dyes, such as transition metal complexes as disclosed in U.S. Pat. Nos. 5,997,622 and 6,001,161, i.e., a transition metal complex of an 8-heterocyclylazo-5-hydroxyquinoline; phthalocyanine dyes such as C.I. Direct Blue 199; anthraquinone dyes, or anthtapyridone dyes.
The water insoluble dyes used in this invention can be any dyes that are insoluble but dispersible in water as disclosed in U.S. patent application Ser. No. 09/510,879, filed Feb. 23, 2000.
In another preferred embodiment of the invention, the water insoluble dyes can be salt-type dyes as disclosed in U.S. patent application Ser. No. 09/709,078, filed Nov. 10, 2000.
The dye used in the ink jet ink of the invention is present in any effective amount, generally from about 0.1 to about 10% by weight, and preferably from about 0.5% to about 6% by weight.
The hyperbranched polymer used in the invention is present in the ink jet ink generally from about 0.1% to about 30% by weight, and preferably from about 0.5% to about 10% by weight.
A humectant is employed in the ink jet composition of the invention to help prevent the ink from drying out or crusting in the orifices of the printhead. Examples of humectants which can be used include polyhydric alcohols, such as ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, tetraethylene glycol, polyethylene glycol, glycerol, 2-methyl-2,4-pentanediol 1,2,6-hexanetriol and thioglycol; lower alkyl mono- or di-ethers derived from alkylene glycols, such as ethylene glycol mono-methyl or mono-ethyl ether, diethylene glycol mono-methyl or mono-ethyl ether, propylene glycol mono-methyl or mono-ethyl ether, triethylene glycol mono-methyl or mono-ethyl ether, diethylene glycol di-methyl or di-ethyl ether, and diethylene glycol monobutylether; nitrogen-containing cyclic compounds, such as pyrrolidone, N-methyl-2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone; and sulfur-containing compounds such as dimethyl sulfoxide and tetramethylene sulfone. A preferred humectant for the composition of the invention is diethylene glycol, glycerol, or diethylene glycol monobutylether.
Water-miscible organic solvents may also be added to the aqueous ink of the invention to help the ink penetrate the receiving substrate, especially when the substrate is a highly sized paper. Examples of such solvents include alcohols, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, t-butyl alcohol, iso-butyl alcohol, furfuryl alcohol, and tetrahydrofurfuryl alcohol; ketones or ketoalcohols such as acetone, methyl ethyl ketone and diacetone alcohol; ethers, such as tetrahydrofuran and dioxane; and esters, such as, ethyl lactate, ethylene carbonate and propylene carbonate.
Surfactants may be added to adjust the surface tension of the ink to an appropriate level. The surfactants may be anionic, cationic, amphoteric or nonionic.
A biocide may be added to the ink composition of the invention to suppress the growth of microorganisms such as molds, fungi, etc. in aqueous inks. A preferred biocide for the ink composition of the present invention is Proxel(copyright) GXL (Zeneca Specialties Co.) at a final concentration of 0.0001-0.5 wt. %.
The pH of the aqueous ink compositions of the invention may be adjusted by the addition of organic or inorganic acids or bases. Useful inks may have a preferred pH of from about 2 to 10, depending upon the type of dye being used. Typical inorganic acids include hydrochloric, phosphoric and sulfuric acids. Typical organic acids include methanesulfonic, acetic and lactic acids. Typical inorganic bases include alkali metal hydroxides and carbonates. Typical organic bases include ammonia, triethanolamine and tetramethylethylenediamine.
Additional additives which may optionally be present in the inkjet ink composition of the invention include thickeners, conductivity enhancing agents, anti-kogation agents, drying agents, and defoamers.
The ink jet inks provided by this invention may be employed in ink jet printing wherein liquid ink drops are applied in a controlled fashion to an ink receptive layer substrate, by ejecting ink droplets from a plurality of nozzles or orifices of the print head of an ink jet printer.
Ink-receptive substrates useful in ink jet printing are well known to those skilled in the art. Representative examples of such substrates are disclosed in U.S. Pat. Nos. 5,605,750; 5,723,211; and 5,789,070 and EP 813 978 A1, the disclosures of which are hereby incorporated by reference.
The following example illustrates the utility of the present invention.